By the Treaty of Venice of 1177, the pope was constrained to recognised Christian as the legitimate archbishop of Mainz, but Conrad was compensated with the archdiocese of Salzburg (as Conrad III). Conrad never, however, ceased to regard himself as anything but the rightful archbishop of Mainz. When Christian died in 1183, Conrad could again assume his archiepiscopal responsibilities in that city, which, in 1160, had been deprived by the emperor of its charter for the murder of the archbishop Arnold of Selenhofen. The fortifications had then been levelled, but Conrad rebuilt them and renovated Mainz Cathedral.

As Cardinal-Bishop of Sabina, he signed the papal bulls issued between March 18, 1166 and November 6, 1199. After the election to the papacy of Cardinal Ubaldo Allucingoli (Pope Lucius III) in 1181 he became new dean of the Sacred College of Cardinals.